Guide to marine electronics

How many pixels do you need? How big is your screen? What are the best range and sensitivity settings? Should you zoom in, zoom out or go for auto? Where is your transducer? How powerful is it? And, most importantly, where are the fish? So many questions, so many options. These days, if you want to catch fish from a boat, your best chance is by using one of the many depth sounders, or ‘fish-finders’ as they are now more commonly called. The science behind these units is developing almost by the hour as they become more sensitive, accurate and incorporate more and more features. Which invariably results in more complexity. In addition, many manufacturers now offer multi-tasking so that your fish-finder can double as your chartplotter/GPS. For the novice boatie, knowing what to look for in a fish-finder is as important as knowing which rig to use and what sort of bait to buy.

We recently had the opportunity to jump aboard Furuno’s new project boat, a Cruise Craft Explorer 625 with enough electronics to equip a small battleship. Apart from a full dash of screens, Cruise Craft pulled out all stops and maximised the bilge space to fit in a brace of transducers.

We spent a day out on the water on the new craft and came away mighty impressed with its fish-finding capabilities. We also used the opportunity to sample the equipment in a variety of ways in order to better explain the latest developments in fish-finding electronics, what to look for in a fish-finder and how they can be used for maximum effect.

It should be noted that there is a wide variety of systems on offer from various manufacturers, but many share the same fundamental operating systems, terminology and graphics. The differences are in the number of features offered, size of display, power, and price.

First off, you have to decide exactly what it is you really need in a sounder. For instance, if you’re typically bottom-bouncing in deep water, you might want to look at the top end of the range, as these units will likely offer more accurate identification of fish and deep-water features. But then again, the same units might be just as useful for sorting whiting from weed and reef in shallower situations. You also need to consider the layout of your boat when it comes to the optimum placement for the transducer and screen.

To cover what can be a very complex and confusing subject, we’ve broken our guide down into three parts: advice on what to look for when buying a fish-finder, how to use them once you’re out on the water and a general buyers guide featuring some of the latest systems on offer.

We begin by discussing what features you might want to look for when you’re shopping for your new fish-finding weaponry.

Resolution is the most important feature to consider when buying and one that has a number of aspects:

• Pixel count: You need to obtain the highest possible pixel count in the vertical format. Horizontal pixel count merely gives a history of what has gone beneath the boat before it falls off the end of the screen and is lost forever. The vertical pixel count, if it is high, offers better resolution. There is no excuse not to have 480 vertical pixels in this day and age for a unit price of around $600.
• Screen size: Basically, the bigger the better, budget allowing. If you are a bottom-bouncer and spend a lot of time at the transom, get a screen that is big enough to see from where you stand and fish. Small screens are too hard to read at the best of times and near impossible to read at speed over bumpy water.
• Screen colour: It should be bright and contrast well against the images displayed. The more colours the screen can display, the more detail you’ll see.
  
• Backlighting: This should also be bright. The cold cathode-lit screens are far easier to read than bulb-lit screens, which tend to be on the amber side of the colour spectrum.
  
• View-ability: The screen should be easily viewed in direct sunlight and while wearing Polaroid or similar quality sunglasses. Make sure the screen can be viewed from the angle that you will use it most. Beware, some units simply ‘black out’ when viewed from side angles.
  
• Colour vs monochrome: Colour screens with good resolution are superlative, making viewing easy and will show much more refined information. Having said that, there are a lot of colour screens on the market that are very basic and are not capable of showing images as they should be seen. Don’t get sucked into buying a colour unit just because it’s colour. If it doesn’t offer the resolution that you require after reading the above, abandon it for a quality monochrome unit. A high-resolution monochrome screen will beat a lousy quality colour screen hands-down, without fail.
  

Fundamentally, you need to do your homework before buying. Ask as many questions as you can, speak to other boaties, check out some of the web fishing forums and, most importantly, set a realistic budget. Like most things, the more you spend, the more you get. But then again, some people aim too high and end up with a high-powered, feature-packed fish-finder, but only need to use a fraction of its capabilities.

Transducers are arguably as important as the screens, because they transmit and receive the signal, which is then sent to the screen/unit for interpretation and display. The power, type and location of the transducer can make all the difference in the world to the accuracy and usefulness of what you see on the screen.

The most common frequencies across the board for transducers are 200 and 50kHz. They are available in stand-alone frequency or, more commonly, in a combination of the two. Generally, 50kHz is used in deep water applications as the lower frequency has greater penetration through water. The downside is that a 50kHz transducer will deliver less on-screen information. In fact, theoretically it will show you only a quarter of the information of the 200kHz unit. Ideally, if you’re looking for bait, small structure and fish down deep, 200kHz should be used until it runs out of power to return a readable signal. You can then take the option to switch over to 50kHz.

Keep in mind that other factors, such as turbulence and water clarity and quality can have an affect on what you see on the screen, how well the signal penetrates the water and to what depth. (When referring to depth, for reference purposes in this article, anything 200m or more is considered ‘deep’.)

Transducer power output is measured in Watts and kilowatts. You will see references in literature to so many Watts “peak-to-peak” and so many Watts “RMS”. If you divide peak-to-peak Wattage by eight, you will arrive at the RMS specification. In a basic unit that might cost $400, you might have 1500 Watts peak-to-peak, while a $1,200 unit might offer 2400 Watts peak-to-peak. But the difference in the capability of the unit can be measured in hundreds of metres. Also, you must remember that, if you are not reading the bottom, the unit will not a have a reference point and therefore will show you nothing between your boat and the sea floor.

Transducers are available in shoot-thru hull, bolt-thru hull and transom-mount configurations. Transom-mount units are by far the most common applications for trailerable boats. Ideally, a transducer should ‘look’ directly down, its beam fanning out in an expanding cone shape. But in practice, some units are positioned/aimed so that their beam is angled slightly, often toward the front of the boat. What this means is that objects/fish that enter the beam on the forward side of the beam may look different on-screen to the same objects/fish that enter at the rear of the beam. In addition, boat movement adds another variable. As the boat rocks fore and aft and side-to-side, the beam is constantly redirected, the movement having its own effect on the screen image.

You also need to appreciate that detected objects first appear on the right side of the screen and gradually scroll off to the left. Therefore, if you’re sounding or trolling for fish, you need to keep your eye on the screen and try and react quickly if you see something, it may be gone by the time you place your lures or bait. Generally, when you have the ‘Fish ID’ function turned off, fish will often appear as arches or parts of arches or perhaps ‘blobs’ with rounded tops.

Every different brand of depth sounder deciphers images and displays them differently. If you are using a unit that is capable of showing arches, the closer the target is to the middle of the beam, the more arched they’ll appear, flattening out as they cross further from the centre. And even a big fish might only show as a small shape on the screen if it happens to be at the outer edge of the beam. Ultimately, it is only by experience, in a variety of conditions and using different screen settings, that you will become familiar with what your screen is really telling you and be able to accurately identify what’s down below.

If searching for pelagic fish very close to the surface, a reduced sensitivity/gain level will clear the screen near the top, but remember that by reducing that sensitivity, the unit will be less effective at greater depths. In other words, by narrowing the sensitivity, you might be missing out on the action just a little further down.

Then again… In deep water, 100 per cent sensitivity can be the ideal, as long as the clutter isn’t too dense near the bottom. If searching for fish and structure at depth, maintain the highest possible sensitivity to get the very best out of your unit.

There are some great innovations happening in the marine industry and none of the electronic companies are resting on their laurels.

In 2008, Navico is introducing a Network Sounder system for Lowrance units, which it claims will allow low-powered transducers (below one kilowatt) to be used in very deep water. An outlay of around $999 will be much more palatable than the $1,400 currently needed for a one kilowatt transducer – let alone the increased cost of the unit needed to drive such a transducer.

Simrad now uses 1kW transducers with ceramic elements on some models, which it claims can be used in waters up to 1800 metres deep.

Furuno has a wide range of transducers up to 3kW and has recently catered to the small trailer boat angler with the introduction of the FCV-585 and 620 models. And, no doubt, 2008 will see a host of new models from many of the marine electronics manufacturers.

But the basics remain largely unchanged. If you’re serious about your fishing, you need to keep abreast of developments in fishing electronics and, more importantly, you need to know what your fish-finder is telling you and how to optimise its effectiveness. Getting to know your fish-finder will result in more productive time on the water and less cost and time spent chasing fish.